1. Field of the Invention PA1 2. Description of the Related Art
The present invention relates to a composition for a sliding member which is suitably used for a portion for which heat resistance is required, as well as a sliding member and a spherical annular seal member using the composition. In the present invention, the sliding members include, among others, bearing bushes and slide plates which are used in portions for receiving load in various machines and sliding in the same, as well as spherical annular seals which are used in, for instance, spherical joints of automobile exhaust pipes, for which a hermetically sealing function is required in addition to the function of receiving load and sliding.
Conventionally, metal materials, nonmetal materials such as graphite or ceramics, compound material such as cermet, and heat-resistant plastic materials such as polytetrafluoroethylene (PTFE) and polyimide resins are known as materials of this type of sliding member. These materials are respectively heat resistant, but problems remain under dry frictional conditions in that the materials have a drawback in friction and wear, that there are shortcomings in their mechanical strength, particularly in impact strength, and that their affinity with mating members is not necessarily satisfactory.
To overcome these problems, as disclosed in U.S. Pat. No. 1,137,373 and Japanese Patent Application Publication No. 23966/1969, sliding members have been developed in which expanded graphite obtained by subjecting graphite to special treatment is formed together with reinforcing members such as metal fibers or the like. Although these sliding members are heat resistant and excel in their affinity with mating members, the sliding members have a drawback that they sometimes generate abnormal noise during sliding under dry frictional conditions.
In addition, although Japanese Patent Application Laid-Open No. 33267/1982 discloses a sliding member which is formed by press-forming a mixture of graphite and metal fibers, this sliding member has a drawback in that they also sometimes generate abnormal noise during sliding under dry frictional conditions.